A high voltage integrated circuit (IC) may include a metal-oxide-semiconductor field effect transistor (MOSFET) that includes a high-voltage field effect transistor (HVFET). Many HVFETs employ a device structure that includes an extended drain region that supports or “blocks” the applied high-voltage (e.g., 150 volts or more) when the device is in an ‘off’ state.
The operating characteristics of a high voltage IC are typically set by a method known as trimming. More specifically, trimming may involve selectively closing (or opening) one or more electrical elements to adjust certain characteristics of the high voltage IC. During the process of trimming, one or more anti-fuses may be shorted to set certain operating parameters in the high voltage IC. An anti-fuse is an electrical device that is normally in an ‘open’ or non-conducting state. To change the state of the anti-fuse to a ‘closed’ or conducting state, a certain voltage and/or current is applied to breakdown the anti-fuse. After breakdown, a substantial current may pass through the anti-fuse.
By way of example, one or more anti-fuse elements may be utilized to trim or program an analog parameter, e.g., switching frequency in a high voltage IC used in a switch mode power supply. During a start-up condition, the high voltage IC may need to read the state of the anti-fuses to make appropriate adjustments to operate within specified parameters.